1. Field of the Invention
This invention relates to a vulcanizable composition and more particularly, to a room temperature vulcanizable silicone rubber composition which is capable of yielding a vulcanized product having good characteristics with respect to water resistance, adhesion in hot water, resistance to LLC (long life coolant), resistance to engine oil and releasing properties and the like.
2. Description of The Prior Art
Room temperature vulcanizable compositions chiefly composed of silicones have wide utility in various fields such as of sealing materials for building, adhesives, sealants such as a gasket of automobile, coatings and the like.
The characteristics required for the room temperature vulcanizable composition mainly composed of silicones recently become more severe. For instance, with respect to sealing materials for buildings, a so-called structure glazing technique wherein a heat ray reflective glass is sealingly bonded to outer walls by the use of a silicone sealing material has been developed, or applications as a sealing material in contact with water is increasing. This requires the use of such a silicone composition under more severe conditions. In particular, there is the demand for improving the durability of adhesion.
In the field of gas sealants for automobile, the range of their application is extended, so that the properties such as resistances to engine oil and LLC are required to be more improved.
Other industrial fields in which room temperature vulcanizable silicone compositions are applied include, for example, the field of a releasing agent which is used as a coating for rolls in copying machines. Since full color copies are increasing in number wherein color shift in image has to be prevented, it is necessary to further improve the releasing properties of rolls for copying machine.
To impart practical mechanical strength of the room temperature vulcanizable silicone composition, the usual practice is to use an aerosil silica filler for reinforcement along with diorganopolysiloxane.
Typical examples of the silica filler include fumed silica which has been treated with trimethylchlorosilane or hexamethyldisilazane, or fumed silica which has been treated with dimethyldichlorosilane or dimethylpolysiloxane.
However, the use of these fillers is not satisfactory in obtaining characteristic properties, such as resistances to hot water, oil and LLC, which are recently strongly demanded in the art.
The silicone rubber compositions of the type stated above are described, for example, in Japanese Patent Publication Nos. 47-30422 and 40-19178. Japanese Patent Publication No. 47-30422 describes a silicone rubber composition which comprises a hydrophobic silica filler having the surface blocked with triorganosiloxy groups of the unit formula, R.sub.3 SiO.sub.0.5, in which R is a monovalent hydrocarbon group, and an organopolysiloxane of which the molecular chain terminals are blocked each with a silanolic hydroxyl group.
Japanese Patent Publication No. 40-19178 describes a silicone rubber composition which comprises a reinforcing filler, an organopolysiloxane having silicon-bonded vinyl groups at the molecular chain terminals and a nitrogen-containing organosilicon compound.